Identification of the mitochondrially encoded subunit 6 of F1FO ATPase in Trypanosoma brucei

- A6, a mitochondrial subunit of F1FO ATPase encoded by pan-edited mRNA in Trypanosoma brucei, for long time had eluded direct identification due to its extreme hydrophobicity.
- This subunit is detected by chasing a mitochondrial translation product into the ATPase complex.
- A partial N-terminal amino acid sequencing of the matching protein in Leishmania tarentolae has confirmed the presence of A6 in purified F1FO ATPase.

Kinetoplast maxicircle DNA of trypanosomatids encodes eighteen proteins. RNA editing is required to confer translatability to mRNA for twelve of these. Sequence conservation of the predicted hydrophobic polypeptides indicates that they represent functional components of the respiratory chain. Yet, so far only two of those, cytochrome c oxidase subunit I and apocytochrome b of cytochrome c reductase, have been identified with biochemical methods. Here we report on identification of A6 subunit of F1FO ATPase encoded by a pan-edited mRNA in Trypanosoma brucei. The polypeptide was present among the 35S-labeled mitochondrial translation products characterized by anomalous migration in denaturing 2D gels. It was identified as an ATPase subunit by co-migration with this complex in Blue Native 2D gels. A partial N-terminal sequence of the corresponding polypeptide present in the gel-purified ATPase complex from Leishmania tarentolae was consistent with the predicted A6 sequence.

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